Bushing terminal guard



y 13, 1953 M. BROVERMAN 2,834,829

BUSHING TERMINAL GUARD Filed Dec. 20. 1955 United rates Patent C BUSHING TERMINAL GUARD Michael Brovcrman, Pittsfield, Mass., assignor to General Electric Company, a corporation of New York Application December 20, 1955, Serial No. 554,170

Claims. (Cl. 174-138) This invention relates to a bushing terminal guard, and more particularly, to a protective cap for the terminal end of an electrical terminal bushing.

In the electrical industry it is well known to have a vertical terminal bushing mounted on the tank cover of an electrical apparatus such as a transformer. A high voltage lead is connected to the terminal clamp on the upper terminal end of the bushing. In some instances the tank of the transformer is grounded, and in order to avoid a short circuit to ground by animals spanning the distance between the terminal hardware and tank cover it has been the practice of theelectrical industry to provide insulating material guards for the upper terminal end of the bushing. These prior art guards have several deficiencies such as not substantially completely enclosing or guarding all of the terminal hardware and not being securely connected to the terminal clamp or upper terminal end of the bushing to ensure that the guards are not dislocated by animals or by accident after being installed. Additionally, some of the prior art guards snap on with respect to a petticoat of the bushing and in order to do this they must be elastic or resilient which often requires that they be constructed from compositions which do not have good weathering characteristics.

Accordingly, it is an object of this invention to provide a guard for the terminal end of an electrical terminal bushing which will substantially completely surround and enclose said terminal end and which is adapted to be securely fastened with respect to said terminal end, the securing means being of the type which does not require that the guard or part thereof necessarily be constructed from elastic or resilient material which ma have poor weathering characteristics.

In one form of my invention the bushing terminal guard comprises a hollow roughly cup-shaped electrical insulating material member. The end of the cup-shaped member which is opposite to the wide open end thereof has a small aperture formed therein so that the member can he slipped on to the lead which is to be connected to the terminal clamp of the bushing. After the lead is connected to the terminal clamp the wide open end of the member can be snugly seated on the terminal end of the bushing. A side wall portion of the cupshaped member which is opposite to the threaded end of a clamping bolt of the terminal clamp has an aperture formed therein. An electrically insulated Y plug is adapted to be inserted through the side wall aperture for engagement with said threaded end while the plug still protrudes into said side wall aperture whereby the cup-shaped member is interlocked with respect to the terminal clamp and securely fastened with respect to the terminal end of the bushing.

To aid in positioning the side wall aperture opposite to said threaded end of the clamping bolt: a slotted tab or wall is formed inside of the cup-shaped member. The wide open end of the cup-shaped member will seat on the terminal end of the bushing if the slotted tab straddles said threaded end, and in this position of the cup-shaped member the side wall aperture will be positioned opposite said threaded end.

Additionally, to ensure further secure fastening of the cup-shaped member with respect to the terminal end of the bushing the plug is adapted to clamp the slotted tab between itself and a clamping nut of the terminal clamp. Y

My invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. I

In the drawing Fig. 1 is a perspective view of on form of my invention. Fig. 2 is an enlarged sectional view of my invention taken along the line 22 of Fig. 1. Fig. 3 is another sectional view of my invention taken along the line 3-3 of Fig. 2.

Referring now particularly to Fig. l of the drawing, shown therein is a porcelain or other electrical insulating material terminal bushing 1 which has a plurality of petticoats formed thereon and is vertically mounted on the cover 2 of a tank 3 of an electrical apparatus such as a distribution transformer. A hard rubber or other electrical insulating material roughly cup-shaped member 4 fits over the upper terminal end of the bushing 1 and encloses therein a terminal clamp best shown in Fig. 2. The upper end of the member 4 has a small aperture 5 formed therein for a high voltage lead 6 which is connected to the terminal clamp.

The terminal clamp per se constitutes no part of my invention and broadly comprises an apertured clamping block 7. An eye bolt having an eye portion 8 and a threaded bolt portion 9 extends through an aperture 10 formed in block 7. The insulation stripped lower end of lead 6 fits into the eye of portion 8 and when a nut 11 on the bolt portion 9 is tightened against the block 7 to compress a pair of opposed and slightly conical annular spring elements 12 therebetween the lead 6 is clamped between the portion 8 and block 7.

Before the lead 6 is connected to the terminal clamp the member 4 is slipped on the lead 6 and can be held in the raised broken line position illustrated in Fig. 2 while the lead 6 is being connected to the terminal clamp. After the member 4 is lowered along the lead 6 towards the bushing 1 the lower wide open end of member 4 will seat itself on the upper frusto-conical surface 13 of the upper petticoat of bushing 1. The lower rim of member 4 has a chamfered surface 14 formed thereon for surface contact with surface 13.

In the seated position of member 4 an aperture 15 formed in a side wall portion of member 4 will be disposed opposite to the right-hand end of bolt portion 9 when viewing Fig. 2 since the axis of the eye bolt is horizontally or perpendicularly disposed with respect to the vertically disposed axes of bushing 1 and member 4. A hard rubber or other electrical insulating material plug 16 extending through and while still projecting into the aperture 15 is adapted to be engaged with the bolt portion 9 whereby the member 4 is interlocked with respect to the terminal clamp and the upper terminal end of bushing 1.

A slotted tab or wall portion 17 is formed inside of the member 4 to aid in quickly positioning the aperture 15 opposite to the bolt portion 9. The slotted tab or wall portion 17 is disposed between the apertures 15 and the axis of the member 4 so that when the aperture 15 is positioned opposite to the bolt portion 9 the slotted tab or wall portion 17 will straddle the bolt portion 9. In its properly seated position the lower edge of slotted tab or wallportion 17 will be disposed below bolt portion 9 as seen more clearly in Fig. 3 whereby the bolt portion 9 will be disposed within a blind slot 18 formed in tab or wall portion 17. Preferably though not necessarily the tab or wall portion'17 extends between opposite sides of the member 4 and is an integral portion thereof. Additionally, the tab or wall portion 17 is parallel to the axis of member 4 and in the seated position of member 4 the plane of wall 17 is perpendicularly disposed with respect to the axis of the eye bolt, and the lengthwise direction of the slot 18 is generally parallel with respect to the axis of the member 4. When the member 4 is held by the hand and lowered along the lead 6 toward the bushing 1, one will be able to sense or feel correct positioning of the member 4 by hand by virtue of the slotted tab or wall 17. That is, if lowering of the member 4 is stopped by abutment of the lower edge of tab or wall 17 and bolt portion 9 slight rotation or jiggling of the member 4 will cause the slot 18 and bolt portion 9 to be aligned whereby the member 4 can be still further lowered to its seated position.

The slotted tab or wall 17 can also serve the function of additionally fixing the member 4 with respect to the terminal clamp or upper terminal end of bushing 11, and retaining the plug 16 in its aperture 15 so that there are no loose or falling parts. For instance, the plug 16 is selected to have a sufficiently long length such that while it is still protruding into the aperture 15 it is simultaneously clamping slotted tab or wall 17 between itself and the nut 11. Additionally, the plug 16 is longer than the distance between aperture 15 and tab or wall 17 so that when the member 4 is free of the bushing 1 the plug 16 will abut the tab or wall 17 before it falls out of aperture 15. The plug 16 is retained from falling out of aperture 15 in an opposite direction to that of .toward the tab or wall 17 by an internally'and externally threaded metallic sleeve 19 which has a stop collar 20 thereon which may be an integral part thereofor a snap washer or the like. The stop collar 20 is wider than the aperture 15 so that it will catch on the peripheral portions thereof before the plug 16 falls out of aperture 15.

The outer end of plug 16 has a slot formed therein so that plug 16 can be turned with a screw driver, and member 4 can be completely closed, or it can have a-slot formed therein to facilitate the provision of an external spark gap between the terminal clamp and an adjacently mounted lightning arrester which is an arrangement well known in the art. For instance, about 90 degrees from the aperture 15 the side of member 4 has a slot 21 formed therein which is shielded by a generally Ushaped ba'lile 22 which may be an integral part of member 4. One electrode of said spark gap comprises amernber 23 which is electrically connected to the hardware of the terminal clamp and protrudes through slot 21 into the baille 22. The other electrode of said spark gap may be provided by a member which is connected to said lightning arrester and positioned adjacent to the outer end of member 23 in a manner which will be obvious to those skilled in the art.

While there has been shown and described a particular embodiment of the invention, it will be obvious tothose skilled in the art that changes and modifications may be made without departing from the invention, and therefore it is intended by the appended claims to coverv all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire tosecure by Letters Patent of the United States is:

1. An electrical insulating material hollow member which is adapted to enclose substantially completely an electrical lead clamp therein, said member having an aperture formed ina portion thereof for the passageof an electrical lead theretbrough, an internal tab formed in said member, and another aperture formed in another portion of said member, and an electrically insulated plug adapted to close said another-aperture and simultaneously clamp said tab between said plug and clamp.

2'. An electrical insulating material hollow member which is adapted to enclose substantially completely an electrical lead clamp therein, said member having an aperture formed in a portion thereof for the passage of an electrical lead therethrough, an internal tab formed in said member, another aperture formed in another portion of said member, and an electrically insulated plug adapted to close said another aperture and simultaneously clamp said tab between said plug and clamp, said tab and means on said plug being adapted to retain said plug mounted in said another aperture.

3. An electrical insulating material hollow roughly cup-shaped member which is adapted to enclose substantially completely an electrical lead clamp therein, said member having an aperture formed in a portion thereof for the passage of an electrical lead therethrough, an internal tab formed in said member for aiding in positioning said member about said clamp, another aperture formed in another portion of said member opposite to said tab, an electrically insulated plug adapted to close said another aperture and simultaneously engage said clamp and clamp said tab between said clamp and plug whereby said member and clamp are interlocked with respect to each other, said tab and means on said plug being adapted to retain said plug mounted in said another aperture.

4. A guard for the terminal end of an electrical bushing which has an electrical lead clamp at said terminal end with said clamp having an externally threaded clamping bolt whose axis is generally perpendicularly disposed with respect to the axis of said bushing, said guard comprising a hollow roughly cup-shaped electrical insulating material member adapted to be snugly seated at its wide open end on said terminal end,,another end of said insulating material member having an aperture formed therein for the passage of an electrical lead therethrough to said clamp, and an aperture formed in a side wall of said insulating material member, and an electrically insulated plug adapted to close said side wall aperture and simultaneously threadably engage said clamping bolt while still projecting into said side wall aperture whereby said clamp and insulating material member are interlocked with respect to each other.

5. A guard for the terminal end of an electrical bushing which has an electrical lead clamp at said terminal end with said clamp having an externally threaded clamping bolt whose axis is generally perpendicularlydisposed with respect to the axis of said bushing, said guard comprising a hollow roughly cupshaped electrical insulating material member adapted to be snugly seated at its wideopen end on said terminal end, another end of said insulating material member having an aperture formed therein for the passage of an electrical lead therethrough to said clamp, another aperture formed in a side wall of said insulating material member, and a slotted tab formed in said insulating material member adapted to straddle said bolt and thereby position said another aperture opposite to an outer threaded end of said bolt, and an electrically insulated plug adapted to close said another aperture and simultaneously threadably engage said bolt end to clamp said slotted tab against said clamp.

References Cited in the file. of this patent UNITED STATES PATENTS 883,227 Padden Mar. 31, 1908 1,983,347 Daley et a1 Dec. 4, 1934 2,274,884 Brach Mar. 3, 1942 2,427,008 Lee Sept. 9, 1947 FOREIGN PATENTS 487,456 Great Britain June 21, 1938 

